Weak Value Amplified Precision Terahertz Spectroscopic Detection of Solid and Liquid Glucose Samples

A novel combination of terahertz time-domain spectroscopy (THz-TDS) and weak value amplification (WVA) is employed to quantify the glucose content of various forms, such as glucose thin films with concentrations from 0.01 to 0.10 mg/mL, glucose solutions with concentrations from 0.01 to 0.10 mg/mL, and glucose tablets with mass fraction varying from 5.0 to 10.0%, which drastically outperforms the classical THz-TDS detection technique. The small concentration and mass fraction changes of glucose samples in various forms that are beyond the traditional THz-TDS detection limit can be detected by the introduction of WVA. For glucose thin films and solutions, the minimum detectable concentration difference is 1–2 orders of magnitude lower and 1–4 orders of magnitude lower, respectively, than the previously accessible THz limits. The detectable mass fraction gradient of glucose tablets is comparable to that of previous studies, but the minimum detectable mass fraction in this work is lower. A general theoretical model to describe the preselected and postselected THz sensing system is established, and the polarization-dependent amplitude and phase evolution induced by changes in sample concentration or mass fraction are shown to correlate with the weak interaction between the THz photon and the target molecules in the WVA formalism. It is shown that WVA significantly suppresses the technical noise with respect to the intensity difference signal induced by the changes in sample concentration or mass fraction when the preselection and postselection procedures come into play. These findings may be favorable for highly sensitive THz detection, including minor changes in the parameters of the test object and interactions between biomolecules.